New Z-Axis Extension for Taig ?


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Thread: New Z-Axis Extension for Taig ?

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    Default New Z-Axis Extension for Taig ?

    I just saw this A2Z Z-Axis extension on ebay for the Taig & Sherline mills and I'm not sure how new of a product it really is. Its a bit pricey, but has anyone here put one on a Taig ?

    A2Z Z Column W/Precision Screw-Taig Sherline Mill XTZS - eBay (item 320642743512 end time Feb-12-11 14:58:02 PST)

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    The Taig is really nice, but it is very easy to run out of Z height once the workpiece is in a vise and you have tooling mounted up. Simple drilling of a taller workpiece comes to mind. I can totally see the apeal to this.

    I just kind of wonder why you wouldn't use some linear rails and some tooling plate to make something similar for less $$. The Kerk Leadscrew is nice, probably about $100 of the cost. So you might only be saving a couple hundred bucks making your own system.

    One advantage to linear rails would be you could make the Z saddle custom (wider) so that you could mount Taig or other spindles more easily. Probably wouldn't need to make it this tall either. I think if my Taig was modified for about 10" of Z travel, that would really expand the Taig's abilities in terms of setup and tooling etc..

    The Taig is also weight bound as far as the workpiece, vises, etc. so it' unlikely you would be using the 16" of height for parts that are that much larger before you hit the table's load carrying capacity. It definitely would give you more 'setup' space for tooling etc.. So that is a huge plus. I just wonder if 16" of z travel might be more height than you want i.e. more torque on the column.

    I can't really tell how this attaches to the Taig's square column and that could be a bit of an issue too. Might be sloppy or might be a point of flex -- hard to say withough seeing a better installation example.

    The "taller you make the z column, the more likely you would want an additional stiffening support similar to what others have done as a tramming aid/stiffener to support the z column. Probably end up doing this with any solution that makes the Taig taller in z.

    My solution, was to buy a Grizzly G0704 for about $300 more than this. The G0704 only has 13" of z but it is so much heavier than the Taig and it can surface better/faster since I'm able to use a 2.5" face mill on it. I have the G0704 as a "manual" machine and it is used more than the Taig now for simple non-cnc'd things.

    My Taig is CNC'd and I love it so don't get me wrong, I'm not bashing the Taig. It is just a small desktop, and a fine one at that. Making it too big might ruin something exceptional?

    If anyone has one of these on a Taig it would be great to see pictures of it.

    Ian



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    Default It is pretty new

    I've heard good reports from Sherline users who have swapped parts of their machines for the A2Z extended equivalents. But this is the first one they've made for the Taig. The Kerk screws, which have coarser pitch, do get better speed out of stepper motors (which have better torque at lower speeds, offsetting their relative lack of mechanical advantage.)

    To get more height from your existing Taig, though, have you tried moving the whole Z-axis assembly up a notch? This gives you an extra few inches, without sacrificing much rigidity. If you're going to try this, though, don't do what I did recently to a customer's machine, and simply unscrew the hex-head cap screws that hold it onto the steel column. That used to work with older machines, but Taig seems to have switched screw suppliers, and the new screw-heads, which are just a bit larger and have ridges on them, rub against the leadscrew just a tiny amount as they come out, deforming the edge of the thread slightly. This caused the bronze nut to gall, and essentially destroyed the whole assembly. (Was my face red...)

    Instead, take the sides off the box ways first, which lets you remove the leadscrew assembly, after which it's safe to take the Z-axis bar off the column, move it up, and reattach it. This is especially useful for 4-axis work, where it's easy to run out of Z room.

    Andrew Werby
    ComputerSculpture.com — Home Page for Discount Hardware & Software



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    The Kerk screws, which have coarser pitch, do get better speed out of stepper motors (which have better torque at lower speeds, offsetting their relative lack of mechanical advantage.)
    Actually you get the best performance by matching the stepper motors to the job at hand. With the stock 20TPI leadscrews, small single stack steppers in the 166 oz-in range are nearly ideal. With all of the reduction of the leadscrew accelration and velocity are more important than the motors max torque.

    With the coarser pitch Kerk screws a double stack stepper in the 270 oz-in range would be a better choice. These will have more torque at lower RPMs and are a better match to the leadscrew pitch.

    Using huge 350+ oz-in motors is a waste of time (and money) in either case.

    Jeff Birt


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    Moving the whole Z-axis up a notch is great until you need to work close to the table. The Z-axis being up one notch didn't work when I needed to hold my work in a small fixture (instead of tall vise) and using a fairly short 3/16" endmill in an endmill holder.

    A half notch would be about perfect and would raise the Z leadscrew just enough for a normal screwless vise to fit under the leadscrew.

    Has anyone experimented with making their own taller Z-axis using the same method that Taig does? You can buy ground steel flat stock of the same dimensions used to build the Z-axis. Would there be a major problem with using a RH X-axis leadscrew and nut on the Z-axis instead of the stock LH ones? Obviously you'd need to change the motor rotation.



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    Default I haven't tried that

    Although I suppose it's possible. Why would you have to reverse the screw direction? If you just want a little more headroom, you can slide the whole headstock assembly up about an inch on its dovetail and it will still hold on.

    I basically agree with Jeff about the motor issue; I was generalizing about the speed/torque relationship in steppers, which tend to lose torque as they spin faster. The fine pitch threads in the standard Taig screws require motors that go faster; coarser ones, like the Kerk screws, need more torque but slower RPMs to achieve the same feedrates. Bigger motors have more holding torque, but are less nimble than smaller ones, due to their greater inductance. You need to balance these factors when building (or modifying) any CNC system. I'd be curious to hear how the stock Taig motors (rated at 200 oz-in holding torque) perform on the A2Z Z-axis.

    Andrew Werby
    ComputerSculpture.com — Home Page for Discount Hardware & Software



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    Sorry, I had two ideas in one email.

    If you make a new Z using flat ground stock (under $100 in materials) and still have the ability to run the tool down to the table you would need a longer Z screw. The only longer screw from Taig is the X screw, and that is RH instead of LH.

    alex



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New Z-Axis Extension for Taig ?

New Z-Axis Extension for Taig ?